The present invention relates to side shift mechanisms for earth-working implements, particularly vertical plows, cable laying plows, trenchers and the like. More particularly, the present invention relates to improvements in power side shift mechanisms wherein any one of a plurality of different implement attachments may be mounted on one common side shift frame.
The prior art discloses a number of side shift mechanisms which are powered by fluid operated piston-cylinders and more complex drive systems, such as rack and pinion devices, etc. The prior art has several disadvantages. For impositive drive systems, the lateral shift of the implement is normally limited by the length and stroke of the piston cylinder, and where a relatively large piston-cylinder is utilized, the piston-cylinder is expensive. Positive drive systems are relatively complex, expensive, and subject to mechanical failure, particularly in earth-working environments.
Another problem with the prior art devices is that they are typically limited for use with one implement only. Thus, each implement attachment has its own side shift mechanism which is undesirable economically and means that substantial time and effort must be expended to make any changeovers.
A further problem with prior side shift mechanisms is that the lift cylinders for the main frame are typically located closer to the midpoint of the frame which results in the side shift frame being subjected to bending loads similar to those in a cantilever beam structure whenever the implement is side shifted to an outboard position on the frame. Additionally, the frame is subjected to large twisting or torsional loads from the ground engaging tool, such as a cable plow, which resists the machine's drawbar load at a point well below the surface of the ground. Thus, there has been a need for an improved mounting arrangement which induces a reaction force opposite to that induced by the implement to reduce both the bending moment and twisting moment imposed on the side shift frame.
During the side shifting operation, a relatively large amount of hydraulic hose is required for the implement control piston-cylinders because the hose must be fed out for accommodating the movement of the implement on the side shift frame. Thus, there has been a need for a device that automatically permits large amounts of hose to be fed out or retracted during the movement of the side shifting implement.
A power shift mechanism for earth-working implements which eliminates some of the problems of the prior art is disclosed in U.S. Pat. No. 4,113,031 to Venable assigned to the assignee of the present invention. The present invention is an improvement over U.S. Pat. No. 4,113,031 because it utilizes a laterally slidable plate in combination with a latching mechanism as described hereinbelow which permits various earth-working implements to be mounted on one common side shift frame with a relatively quick method for mounting or removing the attachments. The present invention is also an improvement over the side shift mechanism disclosed in application Ser. No. 57,769, assigned to the assignee of the present invention, because it incorporates the latching mechanism in the movable implement support frame, as will be described, to thereby further simplify the side shift operation.